The present invention relates to improvements in combustion tools, such as the type used for driving fasteners into work pieces. More specifically, the present invention relates to such combustion tools using replaceable fuel cells, also called fuel canisters. As exemplified in Nikolich U.S. Pat. Nos. 4,403,722, 4,483,474, 4,522,162, and 5,115,944, all of which are incorporated by reference, it is known to use a disposable fuel cell for dispensing a pressurized hydrocarbon fuel to a combustion gas-powered tool, such as, for example, a combustion gas-powered fastener-driving tool. Such fastener-driving tools and such fuel cells are available commercially in the United States from ITW-Paslode (a division of Illinois Tool Works, Inc.) of Vernon Hills, Ill., under its IMPULSE trademark, and in Europe from ITW SPIT (another division of Illinois Tool Works Inc.) of Bourg-les-Valence, France. In particular a suitable fuel cell is described in Nikolich U.S. Pat. No. 5,115,944, listed above.
One disadvantage of conventional combustion tools using such pressurized fuel cells fuel canisters is that, as the tool is operated, the fuel in the cell is progressively depleted. As this occurs, the internal fuel cell pressure drops until the cell is empty, or at least empty enough that there is insufficient fuel for further fastener-driving combustion events. Presently, if the tool fails to fire, the users typically remove the fuel cell from the tool to determine whether the empty fuel cell is the cause. An expensive drawback of this practice is that often the tool misfired for a reason unrelated to the fuel cell, and otherwise usable fuel cells are often disposed of.
Another factor in the use of combustion tool fuel cells is that variations in ambient temperature will influence the internal pressure of the fuel cell. As the temperature drops, more fuel is needed for combustion. Conversely, at higher temperatures, less fuel is required, and the fuel cell may have a longer operational life. However, conventional tools are configured so that the fuel-metering valve emits fuel to the tool combustion chamber independent of both the amount of fuel in the fuel cell, as well as operational environmental conditions.
Accordingly, there is a need for an improved combustion tool that provides an indication of the amount of fuel in the fuel cell. In addition, there is a need for an improved combustion tool in which the amount of fuel transmitted to the tool fuel metering valve is variable as a function of the amount of fuel remaining in he cell, and environmental conditions such as temperature.
The above-listed needs are met or exceeded by the present fuel condition monitoring system for a combustion tool. The system determines the level of fuel in the fuel cell by monitoring at least one of fuel pressure and fuel flow between the fuel cell and the tool. Sensed fuel condition data is compared with preset values to determine the amount of fuel remaining in the fuel cell. Upon reaching the determination of fuel level, an indicator is provided for alerting the user as to the amount of fuel remaining in the fuel cell. If desired, a control unit used for making the determination can also control the operation of the fuel-metering valve based on the determination of fuel cell level. An optional temperature sensor is provided for monitoring fuel cell temperature and providing temperature information to the control unit for adjusting the operation of the metering valve in accordance with the temperature information.
More specifically, a combustion tool employing a replaceable pressurized fuel cell includes a fuel condition monitor system for monitoring the condition of fuel in the fuel cell and for indicating the monitored condition to a user. The fuel condition monitor system includes a fuel condition monitor for monitoring at least one of fuel cell pressure and fuel flow from the fuel cell, a control unit connected to the monitor for receiving fuel condition data sensed by the monitor, comparing the sensed data with preset values and determining fuel level in the fuel cell based on the determinations, and an indicator connected to the control unit for providing a user with an indication of the fuel level in the fuel cell.
In another embodiment, a method of monitoring and indicating fuel cell condition of a fuel cell in a combustion tool includes providing a preset series of fuel cell condition values, monitoring fuel cell condition and obtaining current fuel cell condition data, comparing the monitored fuel cell condition data with the preset values, determining the amount of fuel in the fuel cell and providing a signal to an indicator for indicating the amount of fuel in the fuel cell.